At present various types of crimped cut fibers of cellulose, cellulose acetate and other resin fibers either alone or combined in at least one case with activated charcoal are used in cigarette filters. In order that the pressure drop be not excessive requiring the smoker to "pull" on his cigarette this filter must not be too compact or dense. On the other hand it cannot be too loose or the filtering efficiency is lost.
The labyrinth of passageways in the present cellulose acetate filter elements traps a good deal of the tars and nicotine stemning from the cigarette smoke passing therethrough. But gases generated by the complete or incomplete combustion at the tip of the cigarette such as CO.sub.2 gas in the former instance and carbon monoxide in the latter case are passed through in large amounts to be inhaled by the smoker. An ideal form of filter material is one which would not only trap the solid particles resulting from combustion of the tobacco and paper but also some of the gaseous by-products of that combustion such as carbon monoxide.
It is an object of this invention to describe a cigarette filter which (a) traps tars and other solid particles (b) adsorbs some of the combustion product gases such as carbon monoxide (c) partially absorbs moisture (d) does not itself burn and (e) has a moderately rigid foraminous structure. These and other objects of the invention will be more fully described hereinbelow.